Alien Border Patrol

How to play:

Press Up or X to shoot.

Press Down or Z to reload.

Push the illegal space aliens to the top of the screen.

If an illegal space alien crosses the bottom of the screen it has successfully crossed the border and damage is taken on the currently selected border patrol a.k.a Border Patrol Spaceship.

The bigger the ship the more mass it has. Thus, a ship that has greater mass requires a greater amount of bullets to push it back.